The threshold property of the DynamicsCompressorNode interface is a k-rate AudioParam representing the decibel value above which the compression will start taking effect.
The threshold property's default value is -24 and it can be set between -100 and 0.
An AudioParam.
Note: Though the AudioParam returned is read-only, the value it represents is not.
const audioCtx = new AudioContext();
const compressor = audioCtx.createDynamicsCompressor();
compressor.threshold.value = -50;
See BaseAudioContext.createDynamicsCompressor() for more complete example code.